Shemeska
Adventurer
I also don't understand why Planescape's riding roughshod over (or reinterpreting, if you prefer) prior AD&D lore is to be embraced, whereas 4e's doing the same thing must be repduiated.
Constructive versus destructive change. 2e/Planescape added detail onto the 1e AD&D planes for which previously there wasn't a lot of detail in 1e, and the 2e additions by and large didn't replace or invalidate 1e material. 4e on the other hand broadly replaced the 1e/2e/3e cosmology with something very different in broad terms and in many specific instances recycled classic names for things with either only a passing resemblance to the earlier creature as with the eladrin, or for something like the archons, absolutely no connection whatsoever to the original.
There was continuity between the planes of 1e, 2e, and 3e as the same classic cosmology slowly evolved. 4e on the other hand was a radical break with that classic D&D tradition, intending to replace it with something new. That's why it took a beating in its reception.
What sort of cosmologies were there in 2nd ed AD&D that weren't located within the "Great Wheel"?
Much of the topic of trans-cosmology connections comes from 'Guide to the Ethereal' (which IMO was the most awesome thing Bruce Cordell has ever written), and a few other places. The Far Realm was one of them, the unnamed reality of the Keepers another, another whose name escapes me was in the PSMC III, and others were hinted at.